Under the ruling, Thornton remains ineligible to play until Jan. 11 against San Jose. Thornton has been practicing and traveling with the team. Orpik has missed the last eight games because of a concussion sustained in the attack.

Thornton’s next move is to either accept Bettman’s ruling or take the case to a neutral discipline arbitrator. If Thornton chooses the latter route, which is likely, he must do so by next Tuesday. It would mark the first time under the post-lockout process that an independent arbitrator makes a ruling regarding a disciplinary appeal. The arbitrator’s ruling would be final and not subject to review.

“Simply put, this was a bad act with a bad result, and neither will be tolerated in our game,” Bettman wrote in his 12-page decision.

The Bruins released a brief statement saying, “We respect the process including the ability to attend the hearing with Commissioner Bettman in support of Shawn. At this time, we will decline comment until the process is complete and Shawn has exhausted all rights available to him.”

This is the second time a player has appealed a discipline case. Both times, Bettman upheld the decision. Earlier this season, the NHL Department of Player Safety tagged Buffalo’s Patrick Kaleta with a 10-game suspension for hitting Columbus’s Jack Johnson in the head. Kaleta, however, did not seek an arbitrator’s involvement after Bettman’s decision.

Bettman’s decision disclosed specifics regarding the appeal process. Thornton’s appeal took place at the New York office of Proskauer Rose, which includes the NHL among its major clients.

■ Thornton had dressed for 521 regular-season NHL games without ever being subject to supplemental discipline. His clean record distinguished him from repeat offenders such as Kaleta and Raffi Torres.

■ Shanahan was incorrect in concluding that Thornton’s actions were premeditated.

■ Players who committed similar violations were given shorter suspensions.

Bettman’s analysis centered on Section 18.2 of the collective bargaining agreement, which outlines the factors the league considers when determining supplemental discipline. Factors include whether the player violated league rules in an intentional or reckless manner; any injury to the opposing player; whether the player has a history of discipline; and the situation in which the incident took place.

Bettman applied those parameters in rejecting the NHLPA’s three arguments.

First, Bettman acknowledged Thornton’s spotless history. Bettman also wrote that Thornton has a good reputation and is highly regarded around the league. However, Bettman noted that Thornton’s record was the only reason the suspension was not stiffer.

“Given the other factors present here (and discussed above), the suspension could have (and would have certainly) been considerably longer if Mr. Thornton had not had a clean record,” Bettman wrote.

Second, Bettman concluded that Thornton’s actions were premeditated. Thornton was angry about Orpik’s first-shift hit on Loui Eriksson. Eriksson suffered a concussion and hasn’t played since. Later in the first period, Thornton challenged Orpik to a fight, and Orpik declined the invitation.

Bettman wrote that Thornton’s explanations were inconsistent. During Thornton’s initial hearing with Shanahan Dec. 13, the Bruins enforcer denied he had targeted Orpik. Thornton said he was looking for the biggest player in the scrum.

But a week later, during the appeal hearing, Thornton acknowledged he identified Orpik before crossing the blue line. According to video and testimony, Thornton bypassed Pascal Dupuis, targeted Orpik, and performed the indefensible actions: slew-footing the defenseman and punching him twice in the face.

“Interestingly (and disturbingly), Mr. Thornton testified at the hearing that he knew exactly what he was doing and that he was in complete control of his emotions,” Bettman wrote.

Third, Bettman rejected the argument about similar actions resulting in lesser suspensions. The commissioner did not disclose any of the comparables raised by the NHLPA. It’s likely, however, that Ray Emery’s beatdown of Braden Holtby Nov. 1 was used. Emery was not disciplined. Another possible comparable is Ron Hextall’s attack on Chris Chelios in 1989. Hextall received a 12-game suspension.

Bettman wrote that the NHLPA presented comparables with punishments ranging from zero games to 12 games.

Instead, Bettman compared Thornton’s assault to three of the NHL’s darker incidents: Todd Bertuzzi on Steve Moore (18-month suspension), Dale Hunter on Pierre Turgeon (21 games), and Matt Johnson on Jeff Beukeboom (12 games). Bettman acknowledged Thornton’s incident did not have the same level of aggression as the three, but pointed out the similarities and the consequences among the four events.

“Each of those incidents,” Bettman wrote, “involved an approach from behind against an unsuspecting and defenseless player that was, if not premeditated, certainly intentional; that could not be considered to have involved a ‘hockey play’; and that resulted in serious injury to the victim of the action involved.”

. . .

The Bruins assigned David Warsofsky and Nick Johnson to Providence Tuesday. Warsofsky and Johnson are eligible to play in Providence’s game Thursday against Worcester. Either player could be recalled for Friday’s home game against Ottawa.